The present invention has particular relation to the apparatus for thickening pulp and paper stock shown in Seifert et al U.S. Pat. No. 4,722,793, issued Feb. 2, 1988 to the assignee of this application. The apparatus disclosed in that patent comprises, as its major component, a pair of liquid-impervious rolls rotatably mounted in spaced relation on substantially horizontal axes. An endless wire is trained around these rolls in wrapping relation with a substantial portion of the surfaces of each thereof, and means are provided for driving one of the rolls to cause this wire to travel around the rolls while cooperating therewith to define a space mounted by the rolls and the opposed upper and lower runs of the wire.
A headbox is mounted in this space and includes an outlet for the pulp suspension to be thickened which is discharged into the wedge zone defined by one of the rolls and the portion of the wire approaching that roll, whereby this pulp suspension is trapped between the wire and the roll. The rolls are driven at a speed effecting the development of centrifugal force causing liquid to be expressed from between the wire and rolls with the resulting thickening of the pulp carried on the inner surface of the wire, and means are provided to collect and remove this thickened pulp.
The above patent also discloses that in order to guide the wire so that it will continue to travel in a path perpendicular to the axes of the two rolls, the wire may be provided along one or both edges of its inner surface with a strip, e.g. a V-belt, which fits in a peripheral groove in each of the rolls. In the practical development of the apparatus of that patent, however, considerable difficulty was encountered in securing this guiding strip to the wire in a manner which would prevent its separation from the wire under the stresses of use, particularly at the relatively high speeds contemplated for the apparatus, namely speeds as high as 3,000 feet per minute. More specifically, while it would be presumed that this would not be a problem in view of the improvements in recent years in the technology of adhesives, no adhesive could be found for securing such a guiding strip to a woven wire which would hold up for a satisfactory period even under prototype laboratory testing conditions.